1. Field of Invention
The present invention relates to a lancet for taking blood, and more particularly to a safety lancet that has a detachable needle hub in a barrel to prevent the safety lancet from being reused and to ensure a needle on the needle hub protrudes out of the barrel when the safety lancet is used.
2. Description of the Related Art
Generally, when medical personnel take a small amount of blood from patients or examinees, they use a lancet to pierce the patients' or examinees' skin and then take blood. Recently, the lancet that medical personnel use is disposable to prevent patients or examinees from being cross infected by the lancet.
With reference to FIG. 9, a conventional lancet comprises a hollow barrel (40), a needle hub (30) and a sheath (35). The barrel (40) has an open proximal end and an open distal end. The proximal end of the barrel (40) has a narrowed section (41). The barrel (40) near the open distal end has two slots (42). The slots (42) are defined through the barrel (40) symmetrically. The needle hub (30) is mounted slidably in the barrel (40) and has a proximal end, a distal end, an outer surface, a needle (34), a push button (31), two limiting resilient elements (33) and two stopping resilient elements (32). The needle (34) protrudes from the proximal end of the needle hub (30) and faces the proximal end of the barrel (40). The push button (31) is mounted on the distal end of the needle hub (30) and is mounted in the open distal end of the barrel (40). The limiting resilient elements (33) protrude symmetrically from the outer surface of the needle hub (30) toward the proximal end of the barrel (40) and each limiting resilient element (33) has a limiting end. The limiting end of the limiting resilient element (33) contacts the inner surface. The stopping resilient elements (32) protrude symmetrically from the outer surface of the needle hub (30) toward the distal end of the barrel (40) and correspond to the slot (34). Each stopping resilient element (32) has a stopping end. The stopping end is mounted in the slot (42) and is stopped by the distal end of the barrel (40). The sheath (35) covers the needle (34) to prevent the needle (34) from contamination and to prevent the medical personnel from piercing by the needle (34).
When using the lancet, medical personnel detach the sheath (35) from the needle (34) and then push the push button (31) toward the proximal end of the barrel (40). The needle hub (30) moves toward the narrowed section (41) of the barrel (40) and a distance between the limiting ends of the limiting resilient elements (33) is narrowed. The stopping ends of the stopping resilient elements (32) moves along the slot (42). Therefore, the needle (34) is able to protrude out of the barrel (40) to pierce a patient's or an examinee's skin and to take blood.
When thrust applied by the medical personnel is eliminated, the distance between the limiting ends of the limiting resilient elements (33) is enlarged and becomes an original distance before the push button (31) is pushed, so the needle hub (30) moves toward the distal end of the barrel (40) and allows the needle (34) to retract into the barrel (40). However, the stopping ends of the stopping resilient elements (32) move back to be stopped by the distal end of the barrel (40), so the personnel cannot distinguish if the lancet has been used or not. Accordingly, the lancet may be reused to endanger the patients or the examinees.
With reference to FIG. 10, another conventional lancet has a hollow barrel (60) and a needle hub (50). The barrel (60) has an open proximal end, an open distal end and an inner surface. The proximal end of the barrel (60) has a narrowed section (61). The inner surface of the barrel (60) near the distal end has two protrusions (63). The protrusions (63) protrude form the inner surface of the barrel (40) symmetrically. The needle hub (50) is mounted slidably in the barrel (60) and has a proximal end, a distal end, an outer surface, a needle (54), a push button (51), two limiting resilient elements (53) and two stopping resilient elements (52). The needle (54) protrudes from the proximal end of the needle hub (50) and faces the proximal end of the barrel (60). The push button (51) is mounted on the distal end of the needle hub (50) and is mounted in the distal end of the barrel (60). The limiting resilient elements (53) protrude symmetrically from the outer surface of the needle hub (30) toward the proximal end of the barrel (60) and each limiting resilient element (53) has a limiting end. The limiting end of the limiting resilient element (53) contacts the inner surface. The stopping resilient elements (52) protrude symmetrically from the outer surface of the needle hub (50) toward the distal end of the barrel (60) and each stopping resilient element (52) has a stopping end. The stopping ends are mounted between the distal end and the protrusions (63) before the lancet is used.
When using the lancet, the medical personnel push the push button (51) toward the proximal end of the barrel (60). The needle hub (50) moves toward the narrowed section (61) of the barrel (60) and a distance between the limiting ends of the limiting resilient elements (53) is narrowed. At the same time, the stopping ends of the stopping resilient elements (52) are pressed by the protrusions (63) to stride over the protrusions (63). Therefore, the needle (54) is able to protrude out of the barrel (60) to pierce a patient's or an examinee's skin and to take blood.
When thrust that applied by the medical personnel is eliminated, the distance between the limiting ends of the limiting resilient elements (53) is enlarged and becomes an original distance before the push button (51) is pushed, so the needle hub (50) moves toward the distal end of the barrel (60) and allows the needle (54) to retract into the barrel (40). The stopping ends of the stopping resilient elements (52) will be stopped by the protrusions (63), so the push button (51) cannot be re-mounted in the distal end of the barrel (60). Therefore, the personnel are able to distinguish easily if the lancet has been used or not.
However, in one aspect, when the needle hub (50) is pushed, the limiting ends of the limiting resilient elements (53) are pressed by the protrusions (63), so a degree of the thrust will be decreased and a length of the needle (54) protruding from the barrel (60) is shorter than an expected length. Consequently, the lancet may be failed to take blood from the patient or examinee. In another aspect, when the distance between the limiting resilient elements (53) is enlarged, that may cause a strong force to allow the needle hub (50) to move backward. The force may cause the stopping resilient elements (52) to be pressed by the protrusions (63) and to stride over the protrusions (63) again. Therefore, push button (51) of the needle hub (50) will be mounted in the distal end of the barrel (60) again and the needle hub (50) will move back to an original position before the push button (51) is pushed. Accordingly, the personnel still cannot distinguish if the lancet has been used or not and the lancet will still be reused to endanger the patients or the examinees.
To overcome the shortcomings, the present invention provides a safety lancet for taking blood to mitigate or obviate the aforementioned.